Astronomical handbooks in 16th-century South Asia: Analysis of mean planetary motions in the 1520 <i>Graha-lāghava</i> of Gaṇeśa Daivajña

The Graha-lāghava (“Easy [computation] of the planets”; epoch date 1520), is an astronomical handbook, authored by Gaṇeśa Daivajña (b. 1507 CE) of Nandigrāma. This work became one of the most popular astronomical texts of the second millennium in India and gave rise to a new astronomical school of parameters, eponymously known as the “Gaṇeśa-pakṣa.” We analyze the first of the 16 chapters that make up this work, which covers planetary mean positions and velocities, providing a translation and technical commentary of the text. In our exposition, we also invoke two substantial commentaries on this work that were composed in the 17th-century by brothers Mallāri and Viśvanātha, which help clarify and contextualize Gaṇeśa’s contributions. An Appendix to the online edition of the Journal gives the Sanskrit text of the quoted passages.